Devices including arrays of relatively small structures, sometimes referred to as microneedles or micro-pins, have been disclosed for use in connection with the delivery of therapeutic agents and other substances through the skin and other surfaces. The devices are typically pressed against the skin in an effort to pierce the stratum corneum such that the therapeutic agents and other substances can pass through that layer and into the tissues below.
In one approach, a delivery device comprises an active agent that is externally coated onto an array of microneedles and the active agent is delivered directly into the skin after the microneedles breach the stratum corneum. A number of mechanisms may cause the active agent to be removed from the microneedles and deposited in the skin. For example, the active agent may dissolve off of the microneedles when in contact with interstitial fluid. In certain instances the microneedles may be left in contact with the skin for a specified period of time in order to allow sufficient delivery of the active agent.